provide keys for arrays items and add tests #900

All 275 tests pass, 2 skipped in 2m 48s

    1 files ±0   87 suites +1 2m 48s ⏱️ -4s
277 tests +1 275 ✔️ +1 2 💤 ±0 0 ❌ ±0
281 runs +1 278 ✔️ +1 3 💤 ±0 0 ❌ ±0

Results for commit e14ad1b. ± Comparison against earlier commit a9433a8.